The manufacturers of portable equipments (e.g. mobile phones) need to evaluate the loudspeaker membrane displacement frequency response to offer an optimum compensation for its peaking which is the cause of the loudspeaker damage.
The peaking of the loudspeaker membrane displacement is isochronous with the peaking that can be observed in the electrical impedance transfer function of the loudspeaker, so the limiting of the peaking of the loudspeaker membrane displacement can be determined from the electrical impedance response of the loudspeaker.
Therefore, there is a need to monitor a parameter characterizing the electrical impedance transfer function of the loudspeaker in order to limit peaking of the loudspeaker membrane.
A characterization of the electrical impedance transfer function of the loudspeaker can be done during the mobile phone production stage applying a specific pattern to the loudspeaker but, for optimum limiting the peaking of the loudspeaker membrane, the electrical impedance transfer function should be done in real time during the normal listening, to track also the variation of the electrical impedance transfer function of the loudspeaker with the temperature.
In this scenario, loudspeaker architectures are known in the prior art which monitor the current passing into the loudspeaker to characterize the electrical impedance transfer function of a loudspeaker.
A typical loudspeaker architecture comprises a driving circuit arranged to drive a power amplifier of a loudspeaker.
A current detection module is disposed between the power amplifier and the loudspeaker to create a replica of such current to be sent to the driving circuit of the power amplifier. The driving circuit is arranged to estimate the electrical impedance transfer function of the loudspeaker on the basis of the replica of such current and to establish a proper equalization to apply to an audio stimulus in order to limit the current peaking and then the abnormal loudspeaker membrane displacement.
Creating a replica substantially correspondent to the current passing in the loudspeaker is very important in order to drive the power amplifier at the best in order to limit the peaking of the loudspeaker membrane reducing the risk of the damage of the loudspeaker, also during the normal listening.